Then the behavior between Java 8 and 9, with and without configuration, and with and without xml:space="preserve" differs.
This is the most common behavior:

existing indentation remains

new nodes, including CDATA are inline

It can be observed on Java 8 and 9 if the transformer was not configured beyond defaults and regardless of xml:space="preserve".

But when you configure the transformer with OutputKeys.INDENT=yes and indent-amount=4 Java 8 and 9 behave differently.
On Java 8 you get:

existing indentation remains

new nodes are indented according to the settings

CDATA is not indented

On Java 9, though, this happens:

entire document is indented according to settings, including a bunch of spurious empty lines

accordingly, new nodes are indented

CDATA is put onto new lines and indented as well, fundamentally changing the XML!

Furthermore, with further configuration it becomes apparent that xml:space="preserve" behaves differently as well.
On Java 8 it has no effect, on Java 9 it drops us back into the “nothing changes” case described first.